RE: Can't ping bcast address

From: ccie2be (ccie2be@nyc.rr.com)
Date: Sun Mar 13 2005 - 00:09:26 GMT-3


Thanks Brian.

I was trying to figure out a way to modify the config from IE lab 7, ATM,

so that I could ping the local interface, the remote interface and the

directed broadcast address.

If I can't ping the directed broadcast address, wouldn't routing protocols

have a problem forming an adjacency since most of them use multicast

addressing?

Or, because it's a p2p sub-interface, that issue goes away?

Here's the problem I'm trying to figure out:

If I don't use ip unnumbered under the virtual-template, I can't ping the
local interface, but I can ping the directed broadcast.

If I assign the ip address to the virtual-template, I can ping the directed
broadcast, but can't ping the local interface.

So, how should the config be done so that I ping the directed bcast, the
local interface, and of course, the remote interface?

Thanks, Tim

-----Original Message-----
From: Brian Dennis [mailto:bdennis@internetworkexpert.com]
Sent: Saturday, March 12, 2005 9:32 PM
To: ccie2be; Group Study
Subject: RE: Can't ping bcast address

First off what would the broadcast command under the P2P interface have
anything to do with the PPPoA configuration? This command would only
have effect if the IP address was configured under the subinterface and
not the virtual-template interface. Secondly even if the IP address is
configuration under the P2P interface, would the broadcast keyword be
needed?

Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)

bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Saturday, March 12, 2005 3:12 PM
To: Group Study
Subject: Can't ping bcast address

Hi guys,

 

I don't get this. Maybe someone can fill me in.

 

There are a couple of strange things happening.

 

Notice in the debug output below, when I ping the broadcast address, the
debug shows dest address as 255.255.255.255

 

not 54.8.7.255 which is the address I actually pinged. Also, notice
that
ping's to 54.8.7.254 work fine.

 

So, I have 2 questions:

 

Why is the router changing the broadcast address I'm pinging?

 

And, why isn't the ping to the bcast address working?

 

Also, notice that the config does include the broadcast keyword which I
so
often forget.

 

Here's the config:

 

interface Loopback0

 ip address 54.8.7.6 255.255.255.0

!

interface ATM0/0

 no ip address

 no ip route-cache cef

 no atm ilmi-keepalive

!

interface ATM0/0.208 point-to-point

 pvc 0/208

  broadcast

  encapsulation aal5snap

  protocol ppp Virtual-Template1

 !

interface Virtual-Template1

 ip unnumbered Loopback0

 ppp chap hostname ROUTER6

 ppp chap password 0 CISCO

 

 

R6#p 54.8.7.254

 

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 54.8.7.254, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms

 

R6#p 54.8.7.255

 

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 54.8.7.255, timeout is 2 seconds:

.....

 

*Feb 10 21:27:58.687: IP: s=54.8.7.6 (Loopback0), d=255.255.255.255, len
100, un

routable

*Feb 10 21:27:59.735: IP: s=54.8.7.254 (Virtual-Access1), d=224.0.0.10,
len
60,

unroutable

*Feb 10 21:28:00.687: IP: s=54.8.7.6 (local), d=255.255.255.255
(Loopback0),
len

 100, sending broad/multicast

*Feb 10 21:28:00.687: IP: s=54.8.7.6 (Loopback0), d=255.255.255.255, len
100, un

routable

*Feb 10 21:28:02.687: IP: s=54.8.7.6 (local), d=255.255.255.255
(Loopback0),
len

 100, sending broad/multicast

*Feb 10 21:28:02.687: IP: s=54.8.7.6 (Loopback0), d=255.255.255.255, len
100, un

routable

*Feb 10 21:28:04.687: IP: s=54.8.7.6 (local), d=255.255.255.255
(Loopback0),
len

 100, sending broad/multicast

*Feb 10 21:28:04.687: IP: s=54.8.7.6 (Loopback0), d=255.255.255.255, len
100, un

routable

 

TIA, Tim



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